Rapid Tests for Malaria Can Be Improved

The rapid diagnostic tests (RDTs) for malaria vary in terms of specificity and sensitivity among different commercially available diagnostic kits.

Monoclonal antibodies to Plasmodium lactate dehydrogenase (pLDH) have been previously used to format immunochromatographic tests for the diagnosis of malaria, and are found in several of the RDTs routinely used.

The performance of an individual test may simply be due to how it was engineered or whether it is because of the biochemical nature of the pLDH-monoclonal antibody reaction itself. These tests use a wicking strip with immobilized antibodies to a particular antigen. Infected blood is wicked up the strip and the presence of the antibody-captured antigen is revealed with a colored bead or colloidal gold, which is conjugated to a second antibody that also binds the antigen of interest.

A series of systematic studies was undertaken by several entities including scientists at Access Bio, Inc. (Somerset, NJ, USA) to determine how various pLDH monoclonal antibodies work in combination. Different combinations of anti-pLDH monoclonal antibodies were used in a rapid-test immunochromatographic assay format to determine parameters of sensitivity and specificity with regard to individual Plasmodium species. Dramatic differences were found in both species specificity and overall sensitivity depending on which antibody is used on the immunochromatographic strip and which is used on the colorimetric colloidal-gold used for visual detection.

The authors concluded that a panel of monoclonal antibodies against Plasmodium lactate dehydrogenase could be used in various combinations to identify uniquely all species of malaria parasites that infect humans. Their results demonstrated the feasibility of different test formats for the detection and speciation of malarial infections. In addition, the data will enable the development of a universal rapid test algorithm that may potentially provide a cost-effective strategy to diagnose and manage patients in a wide range of clinical settings. The study was published online on August 1, 2011 in the Malaria Journal.

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